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Question

By Interchanging the given two numbers which of the following equation will be not correct?

3 and 4

This question was previously asked in
SSC CGL 2022 Tier-II (Paper 2 JSO) Previous Year Paper (04-Mar-2023)
The correct answer is

4 × 6 – 3 + 9 ÷ 1 = 25

Understanding the Problem: Interchanging Numbers in Equations

The question asks us to examine four mathematical equations. For each equation, we need to swap the positions of the numbers 3 and 4. After performing this interchange, we must evaluate the modified equation using the correct order of operations (like BODMAS or PEMDAS) and check if the resulting value matches the original result given in the equation. The task is to identify which of the given equations becomes incorrect after this interchange of 3 and 4.

To solve this, we will go through each option one by one, perform the interchange, and then evaluate the equation.

Order of Operations (BODMAS/PEMDAS)

Remember the order of operations to correctly evaluate mathematical expressions:

  • B/P: Brackets/Parentheses first
  • O/E: Orders/Exponents (powers, square roots) next
  • D/M: Division and Multiplication (from left to right)
  • A/S: Addition and Subtraction (from left to right)

Analyzing Each Equation by Interchanging 3 and 4

Option 1 Analysis: Check Equation Correctness

The original equation is: \(3 + 5 \times 4 - 6 \div 2 = 16\)

Now, we interchange 3 and 4. The new equation becomes:

\(4 + 5 \times 3 - 6 \div 2\)

Let's evaluate this using BODMAS:

  • First, perform Multiplication and Division from left to right:
    • \(5 \times 3 = 15\)
    • \(6 \div 2 = 3\)
  • The equation is now: \(4 + 15 - 3\)
  • Next, perform Addition and Subtraction from left to right:
    • \(4 + 15 = 19\)
    • \(19 - 3 = 16\)

The result after interchanging 3 and 4 is 16.

Comparing with the original result (16), we see that \(16 = 16\).

Conclusion for Option 1: The equation remains correct after interchanging 3 and 4.

Option 2 Analysis: Identifying the Incorrect Equation

The original equation is: \(4 \times 6 - 3 + 9 \div 1 = 25\)

Now, we interchange 3 and 4. The new equation becomes:

\(3 \times 6 - 4 + 9 \div 1\)

Let's evaluate this using BODMAS:

  • First, perform Multiplication and Division from left to right:
    • \(3 \times 6 = 18\)
    • \(9 \div 1 = 9\)
  • The equation is now: \(18 - 4 + 9\)
  • Next, perform Addition and Subtraction from left to right:
    • \(18 - 4 = 14\)
    • \(14 + 9 = 23\)

The result after interchanging 3 and 4 is 23.

Comparing with the original result (25), we see that \(23 \neq 25\).

Conclusion for Option 2: The equation becomes incorrect after interchanging 3 and 4.

Option 3 Analysis: Check Equation Correctness

The original equation is: \(3 \times 7 - 8 \div 2 + 4 = 27\)

Now, we interchange 3 and 4. The new equation becomes:

\(4 \times 7 - 8 \div 2 + 3\)

Let's evaluate this using BODMAS:

  • First, perform Multiplication and Division from left to right:
    • \(4 \times 7 = 28\)
    • \(8 \div 2 = 4\)
  • The equation is now: \(28 - 4 + 3\)
  • Next, perform Addition and Subtraction from left to right:
    • \(28 - 4 = 24\)
    • \(24 + 3 = 27\)

The result after interchanging 3 and 4 is 27.

Comparing with the original result (27), we see that \(27 = 27\).

Conclusion for Option 3: The equation remains correct after interchanging 3 and 4.

Option 4 Analysis: Check Equation Correctness

The original equation is: \(9 \times 3 \div 6 + 4 - 8 = 1\)

Now, we interchange 3 and 4. The new equation becomes:

\(9 \times 4 \div 6 + 3 - 8\)

Let's evaluate this using BODMAS:

  • First, perform Multiplication and Division from left to right:
    • \(9 \times 4 = 36\)
    • \(36 \div 6 = 6\)
  • The equation is now: \(6 + 3 - 8\)
  • Next, perform Addition and Subtraction from left to right:
    • \(6 + 3 = 9\)
    • \(9 - 8 = 1\)

The result after interchanging 3 and 4 is 1.

Comparing with the original result (1), we see that \(1 = 1\).

Conclusion for Option 4: The equation remains correct after interchanging 3 and 4.

Summary of Results after Interchanging 3 and 4

Option Original Equation Equation After Interchanging 3 and 4 Calculated Result Original Result Correct After Interchange?
1 \(3 + 5 \times 4 - 6 \div 2 = 16\) \(4 + 5 \times 3 - 6 \div 2\) 16 16 Yes
2 \(4 \times 6 - 3 + 9 \div 1 = 25\) \(3 \times 6 - 4 + 9 \div 1\) 23 25 No
3 \(3 \times 7 - 8 \div 2 + 4 = 27\) \(4 \times 7 - 8 \div 2 + 3\) 27 27 Yes
4 \(9 \times 3 \div 6 + 4 - 8 = 1\) \(9 \times 4 \div 6 + 3 - 8\) 1 1 Yes

Based on our analysis, the equation in Option 2 is the only one that is not correct after interchanging the numbers 3 and 4.

Conclusion

By carefully interchanging 3 and 4 and applying the order of operations (BODMAS/PEMDAS) to each equation, we found that only the equation from Option 2 resulted in a value different from the original equation's result. Therefore, the equation in Option 2 will be not correct after interchanging the given two numbers.

Revision Table: Understanding Interchanging Numbers

Concept Explanation Importance
Interchanging Numbers Replacing one specific number with another specific number wherever they appear in an expression or equation. Changes the values and potentially the outcome of calculations.
Order of Operations A set of rules (like BODMAS/PEMDAS) that dictate the sequence in which mathematical operations should be performed. Ensures consistent and correct evaluation of expressions.
Evaluating Equations Calculating the value of one side of an equation to check if it equals the other side. Used to determine if an equation is true or false.

Additional Information: Solving Equations with Number Swaps

Problems involving interchanging numbers are common in tests of numerical ability and logical reasoning. They require careful substitution and precise application of mathematical rules like the order of operations. When tackling such problems:

  • Read the instruction carefully: Which numbers are being interchanged? Where?
  • Rewrite the expression or equation after the interchange.
  • Strictly follow the order of operations (BODMAS/PEMDAS) during evaluation.
  • Perform calculations step-by-step to minimize errors.
  • Compare the final result with the target value (the original result in this case) to determine correctness.
  • These problems test attention to detail and fundamental arithmetic skills.
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Similar Questions

  1. Read the given statements and conclusions carefully. You have to take the given statements to be true even if they seem to be at variance from commonly known facts. You have to decide which conclusion/s logically follow/s from the given statements.

    Statements:

    All beaches are sand.

    Some deserts are sand.

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    256 * 4 * 9 * 3 * 14 = 51

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  4. Which two signs should be interchanged to make the given equation correct?

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Important Questions from Logical Puzzle

  1. If ‘A’ denotes ‘addition’, ‘B’ denotes ‘subtraction’, ‘C’ denotes ‘multiplication’ and ‘D’ denotes ‘division’, then what will be the value of the following expression?

    6 C (57 B 8) D 7 B 32 A 9

  2. If, 5 + 7 = 47, 3 + 8 = 35, 9 + 2 = 29 then 7 + 4 = ?

  3. Which two signs need to be interchanged to make the following equation correct?

    63 ÷ 21 – 7 + 28 × 3 = 144

  4. If ‘–’ stands for ‘÷’, ‘+’ stands for ‘×’, ‘÷’ stands for ‘–’ and ‘×’ stands for ‘+’, then 80 – 20 + 10 ÷ 8 × 10 is equal to:

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    3 ÷ 2 - 4 × 5 + 5 = 1
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